Method and apparatus for plasma surgery

ABSTRACT

An apparatus for argon-plasma coagulation (APC) is disclosed, in which after activation of the apparatus for APC a specified amount of noble gas flows out of the APC instrument before the high-frequency voltage for ionizing the noble gas is switched on, or can be switched on. As a result an increase in safety is achieved.

[0001] The invention relates to a method and apparatus for plasma surgery.

[0002] Plasma surgery is a form of high-frequency surgery in which a high-frequency electrical alternating current (HF current) is passed through electrically ionized and consequently electrically conductive noble gas (plasma), in particular argon (argon plasma) or helium (helium plasma), and applied to the tissue to be treated in order to produce surgically relevant thermal effects in this target tissue. The noble gas that has most often been used for this purpose is argon, and the best-known thermal effect in the tissue is coagulation, for which reasons this procedure is also known as “argon-plasma coagulation (APC)”. In principle other gases or gas mixtures could be used instead of a noble gas for plasma surgery. For example, for over 50 years air has been used as the gas, in which case the procedure is known as fulguration or spray-coagulation. However, noble gases offer the advantage that they do not cause any chemical effects, i.e. they have a chemically neutral behavior. This advantage can be utilized in particular for the endoscopic application of plasma surgery, where the view would be obstructed by unavoidable smoke formation if air were employed, and the burning or vaporization of biological tissue inevitably associated with the use of air could lead to severe complications, such as the perforation of organ walls.

[0003] For both open incisions and minimally invasive operations plasma surgery has been used for more than 20 years primarily to stop bleeding by thermal means, namely by means of the thermal coagulation of the biological tissue. In this process either the air already present serves as the required gas, as in the case of fulguration or spray coagulation, or a noble gas is used, in which case the procedure is called argon-plasma coagulation because the gas most often used is argon.

[0004] Since catheter-like, flexible instruments have been developed for APC, which can inserted through a working or instrumentation channel of flexible endoscopes (G. Farin et al.: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications; Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 71-77), APC can also be used in flexible endoscopy. It soon became clear that there is a broad spectrum of indications for the APC procedure in this area. Apart from thermal hemostasis, APC is used in flexible endoscopy for tasks such as the thermal destruction or thermal devitalization of pathological tissue (Grund K. E., Storek D., Farin G.: Endoscopic Argon Plasma Coagulation (APC)—First Clinical Experiences in Flexible Endoscopy. Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 42-46). Although the term argon-plasma coagulation (APC) is now too narrow in view of the recent indications for this procedure in flexible endoscopy, and “plasma surgery” would be more suitable, here “argon-plasma coagulation (APC)” will continue to be used for this procedure, but without limiting the procedure to the noble gas argon or to coagulation as the thermal effect.

[0005] The apparatus available since 1992 for application of APC in flexible endoscopy is described in the German patent DE 41 39 029.

[0006] A known problem in employing thermal methods within the gastrointestinal tract, as well as in the tracheobronchial system and the throat region, is the risk that combustible or even explosive substances will be unintentionally ignited. The gastrointestinal tract may contain combustible endogenous gases that can be ignited by the relatively high temperature of the plasma. In the tracheobronchial system the respired gas may have a high oxygen concentration or the patient may even be breathing pure oxygen, so that ignition of combustible substances by the hot plasma can result in an intense fire. Several cases of damage caused in this way are known, both with and without a lethal outcome. Although noble gases cannot cause a fire, damage by fire and/or explosions has been known to occur even when APC is being used.

[0007] The object of the invention is to improve devices for APC in such a way that the ignition of combustible substances is avoided.

[0008] This object is achieved with respect to the method in that after the device for APC has been activated, for example by a pedal or a finger-operated switch, a specified amount of argon flows out of the distal end of the particular APC instrument or APC probe Pr being used, which reduces the concentration of the combustible gas, e.g. carbon monoxide (CO), and/or the concentration of a gas such as oxygen (02) that causes the burning of the combustible gas, to such an extent that ignition of this gas mixture is impossible. In the following, this amount of argon is termed the preliminary argon flow.

[0009] To minimize the time delay At until APC initiation that is caused by the preliminary argon flow, it is useful to make this preliminary flow rate as high as possible; as a rule it can be higher (high) than the flow rate of the argon employed for the APC (low). It can be advantageous here for the amount of preliminary argon to be dependent on relevant boundary conditions; this variation can be achieved either by manual parameter setting before APC is carried out or by a control system with automatic monitoring of the boundary conditions. For example, the amount of preliminary argon can be specified as proportional to the oxygen concentration in the respired gas, or can be automatically controlled or regulated. Similarly, the amount of preliminary oxygen can also be made proportional to the duration of the pause between two or more activations of the procedure and/or to the duration of the activations of APC themselves, by prior adjustment or by a control or regulation means.

[0010] An apparatus suitable for achieving the stated objective consists of an argon source Ar, for instance a gas cylinder, which is equipped with at least one controllable gas valve V and at least one gas-flow sensor Se that can be used for manual setting of both the preliminary argon flow and the flow rate needed for APC. For the automatic control and/or regulation of the preliminary argon flow and/or the argon flow rate needed for APC, the hardware is preferably equipped in addition with control and/or regulation elements Ct. In another embodiment of the invention the hardware also includes electronic memories and processors, which permit programming and a corresponding automatic control and/or regulation of the preliminary argon flow and/or the argon flow rate needed for APC.

[0011] Reference is hereby made to the attached drawings. 

1. Apparatus for argon-plasma coagulation (APC), characterized in that after activation of the apparatus for APC a specified amount of noble gas flows out of the APC instrument before the high-frequency voltage for ionizing the noble gas is switched on, or can be switched on.
 2. Apparatus for argon-plasma coagulation (APC) according to claim 1, characterized in that the amount of noble gas that flows out of the APC instrument before the high-frequency voltage is switched on, or can be switched on, can be adjusted in advance.
 3. Apparatus for argon-plasma coagulation (APC) according to claim 1 or 2, characterized in that the amount of noble gas that flows out of the APC instrument before the high-frequency voltage is switched on, or can be switched on, is dependent on variable boundary conditions.
 4. Apparatus for argon-plasma coagulation (APC) according to claim 3, characterized in that the amount of noble gas that flows out of the APC instrument before the high-frequency voltage is switched on, or can be switched on, is greater, the longer the pause between two periods of activation and/or the shorter the preceding periods of activation have been.
 5. Apparatus for argon-plasma coagulation (APC) according to claim 1, characterized in that during the time interval from activation of the apparatus for argon-plasma coagulation until the high-frequency voltage is turned on, an acoustic and/or visual signal is generated, which informs the user that the high-frequency voltage has not yet been turned on, or that it cannot yet be turned on.
 6. Apparatus for argon-plasma coagulation (APC) according to claim 1, characterized in that the high-frequency voltage is not or cannot be turned on as long as the specified amount of argon has not flowed out of the APC instrument.
 7. Apparatus according to claim 1, characterized in that the apparatus is controlled in such a way that the rate (volume per unit time) at which the noble gas flows out is higher after activation of the apparatus but before the high-frequency voltage is turned on than it is after the high-frequency voltage has been turned on during an APC procedure. 